Known in X-ray imaging for the purpose of taking digital X-ray pictures of an examination object are X-ray detectors that are designed as flat image detectors. Further, X-radiation is converted into electric charge by a scintillator or a direct converter layer, and is subsequently read out electronically by way of active readout matrices. Subsequently, the imaging data representing the examination results are transmitted to an evaluation and display apparatus and further processed for the purpose of compiling images.
The readout matrices include a large number of pixel elements (article entitled “Flachbilddetektoren in der Röntgendiagnostik” [“Flat image detectors in X-ray diagnostics”] by M. Spahn, V. Heer, R. Freytag, published in the journal Radiologe 43, 2004, pages 340 to 350). Since these generally have to be read out, chiefly as regards dynamic X-ray systems, that is to say X-ray systems that compile a series of pictures, at a high frequency such as, for example, 30 images per second and with a high gray-scale resolution, large data quantities arise that are to be transmitted to the evaluation and display apparatus and are to be processed.
The large data quantities can lead to data bottlenecks that, in turn, reduce the rates at which the data are read out and transmitted. The use of more powerful electronic components is complicated and involves high volumes, and is attended by disadvantages such as, for example, high costs or increased production of heat. In order to limit the data quantities and raise the data transmission rates, there are also known X-ray detectors which have predefined zoom stages centered with reference to the imaging surface, and in the case of which only imaging data of the partial imaging surface that targeted in the zoom are transmitted to an evaluation and display apparatus.